1. Field of the Invention
The present invention relates to bill acceptors and, more specifically, to a magnetic verification system for a bill acceptor in which the intensity of light emitted from an LED to a photoresistance is adjusted to cause the photoresistance to change its resistance so that the operational amplifier at the output end of a magnetic induction circuit obtains the correct magnetic field signal value to verify the authenticity of the inserted bill.
2. Description of the Related Art
The magnetic verification systems of regular bill acceptors are commonly adapted to verify the authenticity of bills by means of scanning the magnetic ink of the bills. When verifying different kinds of bills, the resistance value of a variable resistor is adjusted, thereby adjusting the gain of the operational amplifier connected to the variable resistor to produce a different amplification in response to different magnetic field signal values induced by the magnetic device of the system. However, when the ambient temperature changes significantly, the signal output of the magnetic device becomes unstable, and the weak output of voltage potential from the magnetic device, even after adjustment of the gain of the operational amplifier, is not stable enough for recognition, resulting in a false judgment. Further, different elements (magnetic device, operation amplifier) from different suppliers may be different in functioning, affecting the verification operation of the system.